One of the unmeasurables in audio is temporal distortion: most measurements assume a continuous sine wave, and ignore transients. For example, in a two-way loudspeaker with a slow woofer and much faster tweeter, even with "time-alignment", phase shift differences between the woofer and tweeter in the crossover can't be corrected "mechanically". Negative feedback amps magnify temporal distortion by correcting a delayed signal and modifying the output, but the "corrected" signal arrives at the loudspeaker well after the original transient signal that triggered the correction. The result is that the feedback actually creates distortion.

I don't have electronic skill sets, so am unable to do any experiments to confirm or disprove this hypothesis: could some of the electronic / audio prop-heads out there tell me if my observation is correct or not, and why?

Best regards, rdb :-)

As a result, temporal distortion is endemic.

 Just depends on the measurement is all. - jj 21:25:37 11/21/02 (0)
 Re: Temporal distortion - measurable? - john curl 09:41:30 11/21/02 (9)
 Re: Temporal distortion - measurable? - rdellecurti@inwind.it 12:43:11 11/22/02 (3)

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 Just depends on the measurement is all. - jj 21:25:37 11/21/02 (0)
 Re: Temporal distortion - measurable? - john curl 09:41:30 11/21/02 (9)
 Re: Temporal distortion - measurable? - rdellecurti@inwind.it 12:43:11 11/22/02 (3)
 Re: Temporal distortion - measurable? - john curl 08:20:48 11/23/02 (2)
 Re: Temporal distortion - measurable? - robertoamato@mclink.it 04:50:13 11/30/02 (0)
 Re: Temporal distortion - measurable? - RandyB 09:22:11 11/25/02 (0)
 Temporal Distortion - Causes and Cures, by Roberto Delle Curti - RandyB 15:58:10 11/21/02 (4)
 Re: Temporal Distortion - Causes and Cures, by Roberto Delle Curti - john curl 11:04:40 11/22/02 (1)
 Re: Temporal Distortion - Causes and Cures, by Roberto Delle Curti - eico1 10:12:16 11/23/02 (0)
 Re: Temporal Distortion - Causes and Cures, by Roberto Delle Curti - Phil Tower 04:47:35 11/22/02 (1)
 Re: Right, It depends, Phil. - Timbo in Oz 00:09:06 11/25/02 (0)
 Yes, it can be measured.... - John Escallier 06:43:29 11/21/02 (0)

Your speaker crossover, amp questions..I believe the issues are being considered, but would defer to the experts on that.

TTFN, John

Thanks for the background and information on temporal distortion and feedback. I just read a treatise on this topic by Roberto Delle Curti, an Italian electronics engineer and loudspeaker designer, which extends the discussion beyond measurable indicia . .. let me know what you think . . .

Best regards, rdb :-)

• Temporal Distortion Treatise

Things like THD and IMD, measured in the usual way, discard phase, which is the same thing (modulo a factor of 'f') as discarding time.

Things that do a real difference measure time effects just fine. Furthermore, despite a lot of the chatter here, you can use music, tones, MLS, allpass sequences, or anything else as the system input.

JJ - Philalethist and Annoyer of Bullies

To have a good High-End Cable we have to reduce serial inductance and parallel capacitance, leaving the right series resistance that depends on speaker impedance, WF dumping and type of amp output stage.

Type of Wire, type of Shield, type of insulator, type of diameter, type of twisting of wires and of internal wires (there are thousands of combinations) will give the final result. What we use for our Royal Device cables is not even one of the above solutions and our speaker cables are finely tuned for our speakers toward a Tube NO Feedback transformer output amplifier S.E. using good materials without increasing costs to unaffordable levels. We do not make cables just to sell cables, even if we can design cables even for other type of speakers.

The speaker cables are not the least, speaker cable MUST be designed and designed depending on the followings:

1 - type of amp
- feedback or not
- tubes or solid state
- transformer or direct connection

2 - type of speaker
- vented box, closed or back-horn loaded
- horn frontal loading or direct radiation
- number of speakers involved in the total system
- mono or bi-wiring
- multi amp or mono amp system

Who sells you speaker cables without asking anything of the above and without knowing how to approach the problem, this is just a “smart guy” I would say. I am not saying that you won't hear a difference, but surely you won't know if this is really the better "real sound" could come out from that particular system.

Now, if you just go and buy the most expensive speaker cable on the market and connect it to your system without considering the above, you will just be throwing your money out of the window. Although everybody is free to do what he recognizes as the best for his money, you still have to consider the fact that even if you find a lot of funny cables on the market (that cost half of a Cadillac per meter) they have not been proven to improve your system, especially if these are made of “silver “ or “gold” with “proved type of twisting” and other features and benefits, but if you open the small box in between (some cables have), than you will easily find that there is a resistor (or something else) to “re-balance” everything. Strange isn’t it?

Based on this, I would have to conclude that at least some subjectivists and objectivists have both been headed down the wrong path:. (a) the objectivists who claim there are no technical reasons why speaker cables of similar length and gauge should sound different, and (b) the subjectivists who share subjective impressions of cables and attempt to identify which is best (when the suitability of a particular speaker cable, according to Curti, is so system dependent).

thanks for the info you wrote. Some are very interesting.

About: "delay problem is very small..."

I have verified the following:

1 - got a very good F.B. S.S. amp
2 - connect a no crossover speaker 2 ways with only a 24 db filter on TW at 9 KHz acustic cross roughly.
3 - heard the big sound compession on medium frequencies the amp produces compared to a no F.B. TUBE amp

then

4 - connected a 3.3 ohm from amp output to the speaker (speaker is 3.3 ohm coil)..in series to the WF that reproduce most of the spectrum

Now this is what happens:

5 - the acoustic reduction is not that much, still the sound is comparable (as ear sensation) to when the resistor was not there (very small reduction even on base sounding).
6 - the speaker now sounds really (nearby) like to be connected to a NO.F.B. amp.

I know damping has been reduced, due to the higher impedance, but also Backward ElectroMotive Energy has been reduced.
Sound compression normally happens when things are out of phase. So the out of phase seems to be very high. The delay in this case is not due to the length of the cable but to the inertia of the WF, that takes time to move and then to produce energy..

Now the problem could be which one is the cause that makes the speaker sounding so much better: more detail, a Coda piano is really nearly enough at it should, and so on.

Truth is always in the middle..
both of the above are the causes of better sound, less damping and less BEMF to the F.B. loop.

I know it is difficult to divide things.

Another topic on which I am actually working on is: "return loss on connections... between pre & amps or CDP & amps.."

I have in my mind something that tells me that this is another point where we get distortion even if there is a meter of cable.

Having a 100 ohm CDP output & 10 Kohms (or more) PREAMP input, is not as to have as an example output & input impedance the same even if in this second case we lose 6 dBs. The perfect coupling of impedances seems to create good sound. This was also tenth of years ago when transformers were used to couple devices.

Now this also is coherent with the above experiment on the 3.3 ohm in series to the speaker. In this case some hi-range more was present due to the higher Tweeter response, but it was just for test purposes.

if it comes out onto yr mind something else.. please return on the topic..
it is very interesting to go thru..

thanks
Roberto

steve

I would bet that it is different with low feed back SET amps.

Low R is always a good idea anyway :-).

timbo

Thanks very much for the offer, please email the articles to me at:

randyb@ossaudio.com

For future reference, is there a way to locate and obtain articles from AES by the general public, or would one have to apply and be accepted for membership in the AES to do this?

Best regards, rdb :-)